Dear All,
Does anyone know anything of the history of the 'plummet'?
Apparently the plummet was used in Wellington's armies as an
instrument to measure the rate at which soldiers marched. The plummet
was a piece of cord attached to a lead shot that was then used as a
pendulum.
Some approximate values are:
1000 mm plummet was used for 60 steps per minute
600 mm plummet was used for 75 steps per minute
300 mm plummet was used for 108 steps per minute
250 mm plummet was used for 120 steps per minute
(The last of these is probably the most common rate used by military
services today)
As the plummet was in common use in 1812, my question relates to how
long before 1812, this pendulum method was in use for military
marching. If this technique was available in 1790, for example, then
it would have had a significant influence on the metric debate about
whether to use the plummet pendulum or the size of the meridian as the
basis for the length of the metre. This debate centred around Borda
who wanted to market his 'repeating circle' and Thomas Jefferson who
favored the pendulum method because of its universal availability and
its portability; sadly perhaps, Borda won that round!
See http://www.gap-system.org/~history/Biographies/Borda.html where
you will find:
When Borda was made Chairman of the Commission of Weights and
Measures, which had as its members Condorcet, Lavoisier, Laplace and
Legendre, he soon put his accurate surveying instrument to good use.
The Commission was set up in 1790 to bring in a uniform system of
measurement. It considered a proposal which had already been made to
the French government to base the metre on the length of a pendulum
which beat at the rate of one second. This proposal had found favour
with Britain and the United States who considered it a truly
international measure. Borda, however, reported on the 19 March 1791
that the Commission had decided on a different standard, namely that
one metre should be one ten millionth of the distance from the North
Pole to the equator. His argument against the pendulum standard was
that it based one unit on another, which might itself change, and also
that the second itself was an arbitrary unit based on the division of
a day by 12 × 60 × 60. Borda argued that the day should be divided
into 10 hours with an hour divided into 100 minutes each of 100
seconds. Under Borda's leadership the project to accurately measure
the distance from the North Pole to the equator using the Borda
repeating circle was carried out.
Cheers,
Pat Naughtin
Author of the ebook, Metrication Leaders Guide, that you can obtain
from http://metricationmatters.com/MetricationLeadersGuideInfo.html
PO Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
Metric system consultant, writer, and speaker, Pat Naughtin, has
helped thousands of people and hundreds of companies upgrade to the
modern metric system smoothly, quickly, and so economically that they
now save thousands each year when buying, processing, or selling for
their businesses. Pat provides services and resources for many
different trades, crafts, and professions for commercial, industrial
and government metrication leaders in Asia, Europe, and in the USA.
Pat's clients include the Australian Government, Google, NASA, NIST,
and the metric associations of Canada, the UK, and the USA. See http://www.metricationmatters.com
for more metrication information, contact Pat at [email protected]
or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter
to subscribe.
